Cyclotron resonance phototube having axial magnetic field and transverse electric field



United States Patent Inventor Robert J Strain Plaini'ield, NJ. Appl. No. 573,416 Filed Aug. 18,1966 Patented Dec. 22, 1970 Assignee International Standard Electric I Corporation New York, N.Y. a corporation of Delaware Priority Sept. 20, 1965 Great Britain No. 39903/65 I CYCLOIRON RESONANCE PHOTOTUBE HAVING AXIAL MAGNETIC FIELD AND TRANSVERSE ELECTRIC FIELD 7 Claims, 2 Drawing Figs.

0.8. CI. 250/211, 250/4l.9, 250/207, 313/94, 330/4.7

Int. Cl. IIOlj 391-14 Field of Search 250/207,

[56] References Cited UNITED STATES PATENTS 3,231,742 l/] 966 Siegman 250/199 3,247,395 4/1966 Wade 330/47 2,627,034 1/1953 Washburn et aL. 250/41.9(2) 3,23 l ,74l i/l966 Siegman 330/4.7 3,234,476 2/l 966 Sackinger.. 330/4.7 3,371,205 2/1968 Berry 250/4l.9(2)

Primary Examiner-Archie R. Borchelt Assistant Examiner-Martin Abramson Attomeys-C. Cornell Remsen, Jr., Rayson P. Morris, Percy P. Lantzy, Philip M. Bolton and Isidore Togut ABSTRACT: A photocathode at one end of a phototube emits an electron beam having a spiral motion at a cyclotron resonance frequency. An axial magnetic field and transverse DC electric field provide the beam with the spiral motion and the rotational energy is extracted by an output coupler. A collector electrode at the other end, having a DC potential applied thereto, collects the electron beam. A quadrupole amplifler between the field electrodes and coupler may provide improved sensitivity.

III/VI IIIIIIIII/IIIII/III I'll IO,

7/ OUTPUT Ill/I/Il/I/ I/I/I/ III/II I CYCLOTRON RESONANCE PHOTGTUBE HAVING AXIAL MAGNETIC FIELD AND TRANSVERSE' ELECTRIC FIELD I CYCLOTRON RESONANCE rriororusa The invention relates to a cyclotron resonance phototube. The invention provides a cyclotron resonance phototube having an axial magnetic field comprising inaxial order between a photocathode situated at one end of said'phototube and a collector electrodev situated atthe opposite end of said phototube, an anode electrode, means for establishing a transverse DC electric field and an electron output coupler, said anode electrode being electrically coupled to said photocathode such that a potential difference exists between same, and to said collector electrode thereby maintaining it at the same potential.

According to one feature of thein'vention a quadrupole amplifier is interposed between the electron output coupler and said means for establishing the transversepC-electric field.

Theforegoing and other features according to the invention will bev understood from the following description with reference to the accompanying drawings in which:

FIG. 1 shows a cross sectioned side view of a cyclotron resonance phototube.

FIG. 2 shows a cross sectioned side view of a cyclotron resonance phototube with a quadrupole amplifier.

Referring to FIG. 1, a cross1sectioned side view of a cyclotron resonance phototube isshown and comprises a cylindrical outer casel closed at one end, the open end of the 'outer case 1 being provided with a plate'Z which contains the I semitransparent photocathode 3; Supported within the outer case 1 by means not shown are the'anode 4, "twister electrodes and 6, output electron coupler 7 and the collector 8. A magnetic field is providedfparallelto the axis of the phototube. Y

The photocathode 3 is connected-to the anode 4 by an electrical power source Bl,for example,,a-6.to 10 volts battery, thereby providing a potential drop-between the anode 4 and the photocathode 3' to accelerate, the electron beam 11 emitted from the photocathode 3. The anode 4 which is connected to the positive terminal of the power source B1 is also connected to the collector 8 therebymaintaining it at the same potential. A static transverseelectric field is established between the twister electrodes 5 and 6.by way of an electrical power source B2, for example, a-6 to 100 volts battery. The outputelectron coupler 7, for example,a known type electron coupler which will couple out rotational energy of the electron beam, is situated between the'twist er electrodes 5 and 6 and the collector 8 and is connected to the primary winding of a transfonner Tl. -A coupler of this type is described in an article by C. L. Cuccia inthe RCA Review, Vol. l0, Page 270 dated Jun. 1949. The secondary winding of this transformer provides the output for the phototube. The

twister" electrodes 5 and 6 are offset relative to the axis of bunching of the electrons. After receiving an initial velocity betweenthc photocathode 3 and the anode 4, the electron beam 11 passes through the static intense transverse electric field established by the twister" electrodes 5 and 6, this passage being timed by p'roportioning the electrodes, and electric and magnetic fields to last one-half cycle of the cyclotron resonance frequency. In this passage, the electron beam 11 'inenergy and any longitudinal bunching of the electrons within the electron beam 11 is converted into a fast cyclotron wave. The electrons emerge in a synchronous phase relationship and rotate at the cyclotron frequency. By making the electric field established between the twister electrodes 5 and 6 sufficiently high, the effect of transverse noise components may be negated.

This cyclotron wave enters the' output electron coupler 7 and all of the RF. cyclotron energy is extracted and coupled to the output via the transformer T1. To clearly visualize the operation of the output electron coupler'7, the electron energies must be identified. The electron receives energy from the accelerating beam potential which causes it to proceed axially to the collector. This energy will determine the transit time. It receives rotational energy from the transverse field established by the twister electrodes .5 and 6 and it is this rotational energy which induces the alternating current output to be established and passed to the output system via the transformer T1.

Although the system shown in thedrawing according to FIG. ll indicates conventional vacuum tube electrodes, the output electron coupler 7 may be replaced by itswaveguide analogue. Also, because of thesimplicityof the structure, it is possible to use an opaque photocathodfe :3 and illuminate it from the output end of the phototube.

The bandwidth of the phototube 'is limited mainly by the bandwidth of the output electron couples 7, which might be a fewpercent, and the operating frequency would usually be chosen to be in the immediate vicinity of the cyclotron resonance frequency.

Referring to FIG. 2, a cross sectioned side view of a cyclotron resonance phototube with a quadrupole amplifier is shown. The construction of this phototube is exactly the same as the phototube according to FIG. 1 except for the quadrupole amplifier l2, represented by'longitudinal conductors at the corners of a square shapedchannel'. The conductors are situated between the twister electrodes 5 and 6 and the output electron coupler.

, and the fast cyclotron waves entering it. are amplified by the parametric amplificationeffect which does not depend upon the magnitude of the current. The amplified waves pass into the output electron coupler 7 where the 1R.F. cyclotron energy is extracted from the electron beam 11 and coupled to the output as previously described. An amplifier of this type used in conjunction with a fast cyclotron wave is described in an article by R. Adler, G. Urbek and G. Wade, in the Proceedings of the l.R.E., Vol. 47, Page 1713, dated-Oct. i959.

Considerations with regard to the bandwidth of the phototube and its operating frequency are the same as outlined for the phototube according to FIG. 1.

Although the system shown in the drawing according to FIG. 2 indicates conventional vacuum tube components, the

output electron coupler 7 and the quadrupole amplifier 12 may be replaced by their wave guide analogs.

The advantages of these units are: provides efficient narrow band mixing or demodulation of light beams; wide range of operating frequencies; low voltage requirements; compact, rugged structure. I

It is to be understood that the foregoing examples of specific examples of this invention is made'by way of example only and is not to be considered as a limitation on its scope.

Iclaim: I I l A cyclotron resonance phototube comprising anaxial magnetic field disposed along said phototube, said phototube including in axial order between a'photocathode situated at one end thereof, said photocathode emitting an electron beam in response to a light beam impinging thereon, and a collector electrode situated at the opposite end of said phototube for collecting said beam; an anode electrode for accelerating said electron beam; parallel plate electrode means disposed about said electron beam for applying a transverse DC electric field to said electron beam; said transverse electric field and axial magnetic field providing said electron beam with a spiral motion, and an electron output coupler coupling out rotational energy of said beam; direct current supply means connected to said parallel plate electrode means and means establishing a potential difference between said collector electrode and photocathode; whereby said electron beam spiral motion has a predetermined cyclotron resonance frequency.

2. A cyclotron resonance phototube as claimed in claim 1 in which a quadrupole amplifier is interposed between the electron output coupler and said means for applying a transverse DC electric field.

3. A cyclotron resonance phototube as claimed in claim 1 in which said means for applying a transverse DC electric field include a pair of electrodes having said DC electric field therebetween transverse to the direction of the axial magnetic field to provide said spiral motion to said electron beam.

4. A cyclotron resonance phototube as claimed in claim 3 in which the center line of said pair of electrodes is displaced relative to the common center line of the remaining axially spaced components but maintained parallel with same.

5. A cyclotron resonance phototube as claimed in claim 3 in which said electron output coupler includes transformer means to facilitate the extraction of the output from the phototube.

6. The device of claim 3 wherein the electrodes and electric and magnetic fields are proportioned to time the passage of the electron beam through said pair of electrodes to last one half cycle of the cyclotron resonance frequency.

7. The device of claim 3 wherein said anode and collector electrodes are at the same potential. 

